Help:Sizing gallery pictures

When inserting pictures into galleries with the parameter, irregularly sized pictures may result unless all of the images have the same dimensions, leading to a sloppy, unattractive appearance.

To remedy this, choose the image in the gallery with the widest width versus its height (ie, the widest aspect ratio). Divide that image's height by its width and store that value in your calculator's memory. You can now perform either of the following operations:
 * Multiply the gallery's parameter by the value in the calculator, and use that as the new  value.
 * Divide the gallery's parameter by the value in the calculator, and use that as the new  value.

You should now see that all of the images in the gallery have an even presentation.

Process
The second image, File:Perdgate back.jpg, has the widest width relative to its height. By looking at its File page, we see it has dimensions of 750 × 635. Dividing these values gives a ratio of 0.8467.

635 / 750 ≈ 0.8467

The current and  specified in the gallery are 166px and 175px. If we want to favor the larger image dimension (particularly in this case since 200px is a soft minimum used across many small galleries), we will choose to divide 175 by this ratio. This gives a corrected value of 206px.

175 / 0.8467 ≈ 206